1. Field of Invention
This invention relates generally to the field of microelectromechanical (MEMS) devices and, in particular, to floating MEMS devices in which a proof mass is electrostatically levitated.
2. Description of the Prior Art
Microelectromechanical (MEMS) devices are finding ever-increasing areas of application in the modern economy as trends towards miniaturization, portability, lightweight, low power consumption and low cost drive many technologies. Sensors, actuators and many other devices are all affected by the wider application of microtechnology and MEMS fabrication techniques.
The present invention relates to a floating MEMS device (FLEMS) in which a proof mass is levitated electrostatically as part of a MEMS device, without the need for feedback control means and, once levitated, without mechanical contact between the proof mass and any other portion of the device.
This non-contact floating MEMS device of the present invention should be contrasted to prior MEMS devices, particularly accelerometers, in which acceleration is typically sensed by deflection of a proof mass mechanically coupled to the device. Examples include U.S. Pat. Nos. 5,969,848; 5,992,233; 6,067,858; 6,296,779 and 6,250,779.
Electrostatic levitation has been used in a variety of non-MEMS fields of application including non-contact materials processing, acceleration or inertial sensors, and other applications. However, these devices typically require complex means to control and stabilize the position of the proof mass. For example, U.S. Pat. Nos. 5,015,906 and 5,187,399 employ high frequency sinusoidal excitation circuitry for levitation and control. U.S. Pat. No. 4,521,854 is an example of electrostatic levitation requiring a complex sensing and feedback system to maintain the proof mass in its floating position.
In view of the foregoing, a need exists in the art for a floating MEMS device that includes self-stabilizing levitation without requiring sensing and/or feedback systems for controlling the levitation of the proof mass.